Modern semiconductor integrated circuits, or "chips," can be generally divided into two major categories: "microprocessors," which perform logic operations and act generally as the "brains" of electronic systems incorporating them; and "memories," which store data utilized by the microprocessor and other components of electronic systems. Traditionally, memory functions and microprocessing functions have been realized on separate chips. However, semiconductor manufacturers are currently pursuing "embedded" designs that incorporate both memory and microprocessor functions on the same chip. Embedded designs are advantageous because a single chip can take the place of separate memory and microprocessor chips, thus saving needed board space in a final computer product in which it is incorporated. Moreover, embedded chips are expected to produce cost savings, higher reliability, and faster speeds when compared to the use of separate memory and microprocessor chips.
However, the manufacture of embedded designs pose significant challenges. Significantly, the processes traditionally used to manufacture memories and microprocessors are different in ways that make their integration on a single chip difficult. For example, the process used to fabricate a Dynamic Random Access Memory (DRAM) cell array is typically quite different from the process used to fabricate the logic gates of a microprocessor. For example, while memories typically only require two metal levels of interconnections, the logic gates of microprocessor circuitry typically call for many more interconnect levels. Thus, the construction of the embedded memory array on a given portion of the embedded chip product will usually be complete at an intermediate stage of the embedded chip's manufacture. The remainder of the process is directed to the completion of the remaining interconnect levels necessary to complete the logic gates for the microprocessor portion of the chip.
However, because the embedded memory array is covered by the remaining levels used to complete the microprocessor portions of the embedded chip product, access to the array is limited, malking it difficult to directly test the memory using industry standard memory testing techniques. Moreover, the lack of direct array access makes it difficult to use known redundancy techniques to repair any defects within the embedded memory array.
The present inventions are directed to overcoming or at least reducing the effects of the one or more problems set forth above.